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Ch. 4.1 & 4.2

Ch. 4.1 & 4.2. Properties of Aqueous Solutions, Precipitation Reactions. 4.1. Aqueous solutions – solutions in water Can conduct electricity How well it does so is based on # of ions in solution More ions = easier to conduct 3 types of solutions Strong electrolytes Weak electrolytes

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Ch. 4.1 & 4.2

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  1. Ch. 4.1 & 4.2 Properties of Aqueous Solutions, Precipitation Reactions

  2. 4.1 • Aqueous solutions – solutions in water • Can conduct electricity • How well it does so is based on # of ions in solution • More ions = easier to conduct • 3 types of solutions • Strong electrolytes • Weak electrolytes • Nonelectrolytes

  3. 4.1 • (a) Ionic compound dissolving in water • (b) Molecular compound dissolving in water

  4. 4.1 • Ionic compounds • Cations, anions dissociate in water • Each ion surrounded by water molecules • Ions in solution allows flow of current • Pure water doesn’t conduct electricity • Ions in water are what cause people to get electrocuted/shocked (ouch!)

  5. 4.1 • Molecular compounds • Can dissolve, but don’t break apart…so no ions • No ions = no conducting electricity • Ex. Salt water = conductor, sugar water ≠ conductor

  6. 4.1 • Strong vs. weak electrolytes • Strong – completely dissociate (fall apart) in solution • Ex. HCl(aq)  H+(aq) + Cl-(aq) • Weak – partial dissociation, small concentration of ions • Dissociated ions in equilibrium with un-ionized compound • Ex. HC2H3O2(aq) ⇌ H+(aq) + C2H3O2-(aq)

  7. 4.2 • Two solutions (aqueous) mixed and solid is formed • Solid called precipitate • Rxn where precipitate formed = precipitation reaction

  8. 4.2 • Solubility rules – MUST KNOW THESE! • Common Group 1, ammonium (NH4+) salts are soluble • Nitrates (NO3-), chlorates (ClO4-), acetates (C2H3O2-) are soluble (except AgC2H3O2) • Halide salts (except fluorides) are soluble except those of Ag, Hg22+, and Pb • SO42- soluble except with Ag, Hg, Pb, Ca, Sr, Ba • Group 1, Ca, Sr, and Ba hydroxides (OH-) are soluble, the others are typically not • Other ionic compounds = insoluble

  9. 4.2

  10. 4.2 • How will I remember all of those?! • Easier way: solubility song!

  11. 4.2 Rules For Solubility (Taken from Cornell University - Chemistry Department) 
(Sing to Rhythm of 99 Bottles)  Potassium, sodium, and ammonium salts, 
Whatever they may be, 
Can always be depended on 
For solubility.  When asked about the nitrates 
The answer is always clear, 
They each and all are soluble, 
Is all we want to hear.  Most every chloride's soluble 
At least we've always read 
Save silver, mercurous mercury 
And (slightly) chloride of lead. Every single sulfate is soluble,
'Tis said ‘ceptbarium and strontium 
And calcium and lead.  Hydroxides of metals won't dissolve 
That is, all but three 
Potassium, sodium and ammonium 
Dissolve quite readily. And then you must remember 
That you must not "forgit" 
Calcium, barium, strontium 
Dissolve a little bit.  The carbonates are insoluble, 
It's lucky that it's so, 
Or else, our marble buildings 
Would melt away like snow.  (Repeat with feeling) 
Potassium, sodium, and ammonium salts 
Whatever they may be, 
Can always be depended on 
For solubility. …AND YES, WE ARE GOING TO MEMORIZE THIS! YAY! YouTube – Solubility Song

  12. 4.2 • Double Replacement/Displacement (Metathesis) Reactions (…many names, the same thing…) • Swapping of ions • Ex. AX + BY AY + BX • In solution, a chemical change will occur if… • Precipitate forms • Weak electrolyte forms • Insoluble gas forms (it will bubble out)

  13. 4.2 • Molecular equation – all species listed as molecules • Ex. HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq) • Complete ionic equation – lists all ions • Ex. H+(aq) + Cl-(aq) + Na+(aq) + Cl-(aq)  H2O(l) + Na+(aq) + Cl-(aq) • Net ionic equation – lists only unique ions (no spectators) • H+(aq) + OH-(aq)  H2O(l)

  14. 4.2 • To determine if reaction is occurring in solution… • AgNO3(aq) + KCl(aq)  ??? • 1. Separate ions • Ag+ + NO3- + K+ + Cl- • 2. Determine all possible compounds formed • KNO3, AgCl • 3. Determine which (if any) of the compounds will form a precipitate (a.k.a. are insoluble) • KNO3 soluble; AgCl  insoluble • Write your chemical reaction without “spectator ions” • Ag+(aq) + Cl-(aq) AgCl(s)

  15. 4.2 • Your turn! • Write the complete ionic and net ionic equations for the following reactions: • Aqueous solutions of sodium sulfide and calcium nitrate are mixed. • Aqueous solutions of barium chloride and potassium sulfate are mixed. • Aqueous solutions of silver nitrate and ammonium chloride are mixed.

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